Method of making abrasive articles



Nov. a, 1938. w, D, ossow 2,136,022

METHOD OF MAKING ABRASIVE ARTICLES Filed Feb. 10, 1937 2 Sheets-Sheet l INVENTOR.

Walter D.Ro$ s0w.

M WW 3% ATTORNEY-S".

. Nov. 8, 1938. w. D. ROSSOW 2,136,022

METHOD OF MAKING ABRASIVE ARTICLES Filed Feb. 10, 1937 2 Sheets-SheetZ INVENTOR.

Wu Z 201D. Ross-oar.

$020 M7? 2r fwzz ATTORNEYS Patented Nov. 8, 1938 METHOD OF MAKING ABRASIVE ARTICLES Walter D. Bossow, Tiflin, Ohio, assignor to The Sterling Grinding Wheel Company, Tiflin,

Ohio, a corporation of Ohio Application February 10, 1937, Serial No. 125,031 4 Claims. (01. spa-1s) The present invention relates to abrasive articles and more particularly to a method of making abrasive articles having sections of weakly bonded material and/or apertures therein.

An object of the present invention is the provision of a novel method of making an abrasive article having a section of weakly bonded material and/or an aperture therein, wherein a core or the like of weakly bonded material is employed in forming the section of weakly bonded material and/or the aperture.

Another object of the present invention is the.

provision of a novel method of making an abrasive article having an aperture therein, which comprises molding weakly bonded material into the article, which weakly bonded material is subsequently removed to form the article.

Further objects and advantages of the invention will be apparent to those skilled in the art to which the invention relates from the following description of the preferred embodiments thereof, described with reference to the accompanying drawings forming apart of this specification, in which similar reference characters designa e corresponding parts throughout the several vie s, and in which:

g. 1 is a perspective view of one form of abrasi e article embodying the present invention;

Fig. 2 is a perspective view of a mold showing 80 one stage in the production of the abrasive article, shown in Fig. 1, by the methodof the present invention;

Fig. 3 is a section on the line 3-3 of Fig. 2;

Figs. 4 and 5 are sections similar to Fig. 2,

86 but showing further advanced stages in the process. Fig. 6 is a perspective view similar to Fig. 1 showing an abrasive article of modified construction embodying the present invention, and

60 Fig. '7 is a perspective view similar to Fig. 2 but showing a stage in the production of the abrasive article shown in Fig. 6 by the method of the present invention.

According to the provisions of the present invention abrasive articles having desired sections of weakly bonded material and/or apertures therein are formed by molding therein suitable cores or the like, of weak bonded material which cores or the like are eitherallowed to remain in the article to form sections of weakly bonded material or are removed to form apertures.

Fig. 1 shows an abrasive article, in the form of an abrasive disk A. provided with clearance grooves l0 opening into the working surface thereof and K a central aperture ll extending therethrough, all of which apertures were made by suitable cores molded therein during manufacture, and subsequently removed. The abrasive article A shown is of the type adapted for use with a commercially known surface grinder, 5

having a vertical grinding spindle, and has a I plurality of nuts I! embedded therein through the medium of which it can be secured to the grinder spindle.

As shown in Fig, 1, the depth of the clearance 10 grooves 10 is about 85% to 90% of the height of the article. This necessarily weakens the disk to some extent and while the disk shown in Fig. 1 is satisfactory for most purposes, at times a stronger disk may be desired. Fig. 6 shows-a l5 modified construction in which the same arrangement of clearance grooves shown in Fig. 1 is maintained in the working face of the disk with out weakening the disk to the same extent. As

shown in Fig. 6 the clearance grooves l5, which 20 open into the upper or working surface of the abrasive disk B, are only one-half as deep as the clearance grooves 10 shown in the disk A, and are supplemented by rectangular apertures I6 which appear as clearance grooves in the work- 25 ing face of the disk as the disk wears away in use. The apertures l6, which become clearance grooves asthe wheel wears away, are spaced intermediate the grooves l5 and are similar in size and shape. The bottoms of the grooves I 5 are preferably either in the same plane with the top of the apertures l6 or extend slightly below the same so that the apertures I6 come to the work ing surface of the disk at or before the time the clearance grooves l5 disappear.

In both of the preferred embodiments shown in Figs. 1 and 6 the weakly bonded core material has been removed leaving the grooves or apertures l0, l5, and IE, but it is to be understood that the weakly bonded core material may be allowed to 40 remain in the disk if desired. This does not interfere with the operation of the disk as the weakly bonded material wears away faster than the article itself. If the weakly bonded material is of the proper character the disk can be materially strengthened by'allowing the core to remain in position, as will be hereinafter more specifically pointed out.

In the art of making abrasive articles of the type referred to, as commonly practiced, the mix", which comprises suitable abrasive material such as silicon carbide, aluminum oxide, etc., thoroughly mixed with a sufiicient quantity of a suitable binder such as resin, rubber etc., is placed in a suitable mold, subjected to high pressure, and subsequently cured, thus producing a strong bonded abrasive article. In general the method of the present invention follows the aforesaid procedure except that a desired section of weakly bonded material and/or apertures in the finished product are formed by placing suitably shaped cores or masses or weakly bonded abrasive or other material in the mold along with the mix. After the article has been cured the cores are either allowed to remain therein to form the sections of weakly bonded material or are removed leaving the desired apertures. The cores or masses of weakly bonded material do not interfere with the pressing step or operation since being weakly bonded, they compress along with the mix and the result is a finished article of equal density. In the finished article the last mentioned characteristic, that is, equal density, is highly important and cannot be obtained by the use of ri id cores or the like.

Suitable removable cores may be made from abrasive material such as silicon carbide or aluminum oxide weakly bonded with linseed oil or some similar material which will set by the time the cores are used, and which bond will be broken during the pressing operation leaving practically no strength. It has been found that by the time the disk is finished, cores of this character, will be partly, if not entirely, gone and any particles thereof remaining can be readily removed. If the core is to be left in the article thereby forming a section of weakly bonded material therein and the strength of the article thereby increased, the weakly bonded material or core preferably comprises a reversible resin, that is one which never cures at all or only upon prolonged heating. Cores made of abrasive material, such as silicon carbide or aluminum oxide weakly bonded with a small quantity of shellac or a glycerol phthalic anhydride resin, are very suitable for this purpose.

Referring to Fig. 2, the reference character C designates a mold in which the mix l8 and the cores l 9 and 20 are placed and subsequently compressed. The size and shape of the mold will depend upon the article being made and in the present instance consists of a member having a cylindrical cavity therein since it is desired to make a disk-like article. After the core I9 has been properly centered in the cavity of the mold and the nuts I2 correctly located, enough mix" is placed in the mold, which when compressed will just cover the nuts. The cores 20 which as shown, are narrow slabs or strips, are then placed or stood on this base and braced in some suitable manner as by a handful of mix placed on either side thereof. As shown the cores 20 are tangent to the cylindrical core l9 and project radially with respect to the finished article. In the present instance the cores 20 are made of silicon carbide or aluminum oxide boded with linseed oil since it is desired to remove the same from the cured article, thus producing an abrasive disk having opened clearance grooves l0, see Fig. 1.

After the cores have been properly located and braced the rest of the mix'is run into the mold in the usual manner. The amount of loose mix" employed is preferably such that after it is leveled it just-comes to the top of the cores, of slightly covers them, see Fig. 4. The material is then pressed in the usual manner and the cores, being weakly bonded, do not buckle but merely crush down with or withoutan increase in width and are compressed with the rest of the material. Preferably the density of the cores or weakly bonded material is such that itcompresses along with the mix. The extent to which the material is compressed depends upon the density desired in the finished article, but assuming that it is compressed to two-thirds of its former height the cores will likewise be compressed to substantially two-thirds of their former size, see Fig. 5. The compressed articles are subsequently cured in the usual manner and if the loose material of the cores is not thereafter already gone, it is removed. Had it been desired to produce an abrasive article having a section of weakly bonded material therein rather than having opened apertures therein, the core material would preferably have been weaklybonded with a limited quantity of a reversible resin as previously pointed out.

Substantially the same steps are employed in making the article shown in Fig. 6. First the nuts I2 and the cylindrical core l9 are placed in the mold D and enough mix l8 added to just cover the nuts l2 when compressed. The cores 23 which are similar to the cores 20 except that they are only one-half as high, are then placed on this material as a base, and after being suitably braced, enough mix is run into the mold to fill the same to the tops of the cores 23. Thereafter the cores 24, similar in construction to the cores 23, are placed on this material as a base, see Fig. 6, and enough mix run into the mold to just fill the same to the tops of the cores l9 and 24, or slightly cover the same. The material is then compressed in the usual manner and the resultant article cured, after which the loose material of the cores may be removed to leave well defined grooves. During the compression step'the cores 23 and 24 crush down and are compressed in the same manner as the cores 20 referred to before.

Abrasive articles of various sizes and shapes,

having various kinds of apertures therein can be readily produced by the present method. It will also be apparent that abrasive disks with clearance grooves of any desired shape or configuration, and of any depth, can also be formed. While the disks shown are adapted to be secured to the spindle of the grinder with which they are adapted to be used, through the medium of nuts I! embedded in the underside thereof, it is to be understood that the disk may be formed on a steel backing plate, or with bolts or studs embedded therein and projecting from the rear side, or any other conventional means may be employed in at-. taching the same to the machine with which it is to be used.

From the foregoing description it will be apparent that the objects heretofore enumerated have been accomplished and that a new and improved method of making abrasive articles, has been provided. As already stated the invention is not limited to the particular articles shown or the specific steps employed in the preferred manner of practicing the method herein described, all of which may be varied within the scope of this inyention. The term mix as used throughout this specification including-the appended claims, ineludes any suitable mixture of abrasive material and binder employed in making strong bonded abrasive articles. 7

Having thus described my invention, I claim:

1. The method of making an abrasive article having-an aperture therein which comprises placing a suitable weakly bonded core in a mold along with the mix from which the article is made, compressingthe'material thereby crushing the core,

and subsequently curing the compressed material. 2. The method of making an abrasive article thereby crushing the latter, and subsequently .curing the compressed material.

3. The method 01' making an abrasive article having an aperture therein which comprises placing a suitable weakly bondedcrushable core in a mold along with the mix from which the article is made, compressing the material to reduce both the core and the mix in volume, curing the compressed material, and removing the core material.

4. The method of making a solid disk-type abrasive article having a clearance groove in the working surface thereof which comprises placing a weakly bonded'core in the mold along with the material from which the article is to be made, subjecting the material to pressure to compact the same and crush the core, curing the compressed material, and removing the core material.

WALTER 1). Rossow. 

